Means for controlling the dampening of an elastically suspended rotating drum duringcentrifuging



1963 J. F. PRlBONlC ETAL 3,114,705

MEANS FOR CONTROLLING THE] DAMPENING OF AN ELASTICALLY SUSPENDEDROTATING DRUM DURING CENTRIFUGING Filed Aug. 20, 1962 v 2 Sheets-Sheet 1John E Pribqnic BY James E.Whe'lan Their Attorney 1963 J. F. PRIBONICETAL 3, ,705

MEANS FOR CONTROLLING THE DAMPENING OF AN ELASTICALLY SUSPENDED ROTATINGDRUM DURING CENTRIFUGING Filed Aug. 20, 1962 2 Sheets-Sheet 2 INVENTORSUnited States Patent 3,114,705 MEANS FUR COIITRULLING THE DAMPENING OFAN ELASTICALLY SUSPENDED RGTATlNG DRUM DURING CENTRIFUGING John F.Pribonie and James E. Whelan, Dayton, Ohio, assignors to General MotorsCorporation, Detroit, Mich a corporation of Delaware Filed Aug. 29,1962, Ser. No. 218,012 9 Claims. (Cl. 210-145) This invention relates toa domestic appliance and more particularly to a hydraulic shock absorberfor a horizontal tumbling drum or other elastically suspended rotatingsystem.

Washing machines utilizing centrifugal extraction present a problem inbalance. Some of these machines use a rotatable, perforated, clothescontaining cylinder or drum mounted for rotation on a substantiallyhorizontal axis, the clothes being inserted in the drum and rotated atrelatively slow speed in the presence of a washing liquid for washingthe clothes. This wash liquid is subsequently drained from the clothescylinder and the liquid is extracted from the clothes by increasing thespeed of rotation of the drum until the centrifugal force generated bythe increased speed causes the water contained in the clothes to bethrown through the perforations of the drum. Occasionally, unbalanceoccurs due to imperfect distribution of the clothes around the peripheryof the drum. Such unbalance requires that either the machine be securedto the floor or otherwise provided with resilient support properlydamped to assure that excessive machine vibrations will not betransmitted to the floor.

In rotating unbalanced masses, the largest excursions of the rotatingmass occur at What is referred to as the resonant frequency of thesuspended mass. With a clothes spin drum, for instance, the resonantfrequency is some where between 100 and 200 r.p.m. Once the suspendedmass passes through its resonant frequency, the excursions are less andthere is no need for damping action. Actually, all damping which occursin the rotating or vibrating system above its resonant frequency isreflected as additional work required of the drive motor. In otherwords, energy absorbed by the damping or snubbing action of shockabsorbers, for instance, must be supplied by the motor itself. Thus,even though the vibrations above resonant are not sufficient to requiredamping in a washing machine, unnecessary work is being expended withthe prior art devices in controlling these vibrations. The motorsrequired to rotate spin drums in domestic Washers today are sized attheir upper limit, according to U.L. standards, without going intopermanently wired installations. If the spin speeds of drums are to beincreased, a means must be found to reduce motor power requirementselsewhere in the rotating system. This invention, then, is directed to ahydraulic shock absorber for a rotating drum which is effective todampen vibrations only in the range of the rotating drums resonantfrequency and which includes means for effectively eliminating dampingaction above the resonant frequency of said drum, thereby to reduce thepower requirement on the motor when the drum is at its maximum spinspeed.

Accordingly, this invention is directed to apparatus for reducing powerrequired to rotate damped, elastically suspended, vibrating masses abovesystem resonant frequency and of reducing the transmissibility of thedisturbing force.

Another object of this invention is the provision of a shock absorberfor damping the excursions of an elastically suspended, vibrating mass,said shock absorber including a frequency sensitive valve to eliminatethe damping action of the shock absorber only above the resonantfrequency for the vibrating mass.

A more specific object is the combination of an elastically suspended,non-vertical axis, rotating clothes drum with a hydraulic shock absorberhaving a frequency sensitive valve openable during drum acceleration atsome preselected frequency above the resonant frequency of the rotatingdrum to allow the hydraulic fluid to bypass the normal control valves ofthe shock absorber and closable during drum deceleration as saidresonant frequency is approached to permit the control valves of theshock absorber to become effective.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings wherein a preferred embodiment of the present invention isclearly shown.

In the drawings:

FIGURE 1 is a generally schematic rear view of a horizontal axis,rotating drum machine with the back removed to show the generalarrangement of parts;

FIGURE 2 is a generally schematic side sectional view taken along line2-2 in FIGURE 1;

FIGURE 3 is a fragmentary side sectional view of the shock absorber ofthis invention in an at rest position;

FIGURE 4 is a fragmentary side sectional view with the frequencysensitive valve means in one by-pass position during the compressionstroke of the shock absorber; and

FIGURE 5 is a view similar to FIGURE 4 with the frequency sensitivevalve means in another by-pass position during the rebound stroke of theshock absorber.

In accordance with this invention and with reference to FIGURES 1 and 2,a horizontal drum-type combination washer-dryer 6 is shown comprised ofa box-like casing enclosing a generally imperforate cylindrical watercontainer 7 suspended along a top portion thereof by four springs 8 anddamped along its bottom by a pair of hydraulic shock absorbers 9. Aperforate tumbling drum or centrifuging means 10 rotatable about agenerally horizontal axis is rotated by an electric motor .11 through abelt and pulley system 5. Fabrics, such as clothing placed into thetumbling drum 10 through a front access opening in the casing, arewashed when water, admitted by any suitable conventional means, isagitated with the fabrics as the tumbling drum 10 is rotated by themotor 11.

An elastically suspended vibrating mass or system 17, such as the watercontainer 7, tumbling drum 10 and motor 11, usually requires damping toenable the vibrating system to pass through the resonant frequencythereof without causing damage to the component parts of the appliancedue to excessive movement of the system. Such damping or snubbing isaccomplished by installing one or more of the shock absorbers 9 inparallel with the suspension springs 8.

Since snubbing action produces no desirable effect at frequencies abovethe resonant frequency, it would be beneficial to remove part or all ofthe damping force after the operating frequency of the system exceedsits resonant frequency. This would lower the power requirements of thevibrating system and would permit the use of less powerful motors 11.

Referring now to FIGURE 3, the shock absorbing element 9 of thisinvention is comprised of a cylinder 12 closed at the bottom end thereofby a base valve and cap 14 and at the top by a cap 16. An actuating rod13 is journaled in the cap 16, the cap forming a guide for the rod 13.The upper end 15 of the rod is connected to the elastically suspended,vibrating mass 17 comprised of the water container 7, drum 10 and motor11.

An outer cylinder 18 is positioned around the cylinder 12 and has thelower end thereof closed by a cap 20. The cap 20 carries any suitablefitting 21 connectable with the unsprung mass, such as the frame of thecombination washer-dryer 6. The upper end of the outer cylinder 18 haswelded thereto a closure member 22, whereby to provide a reservoir space25 for hydraulic fluid. The reservoir space 25 connects with theinterior of the cylinder 12 through the base valve 14, passages 26 beingprovided for flow of fluid between the reservoir and the interior of thecylinder 12 by the spacing of the caps 14 and 20.

The base valve 14 consists of a valve member 31 which provides for anupward flow of fluid from the reservoir into the interior of thecylinder 12. More particularly, the valve 14 consists of a valve element31 positioned within a valve bore 32 in the closure wall 27, the valveelement 31 having a radially extending annular flange portion 33 thatengages the valve seat 34 to close the valve bore 32. A light fingerspring 35 holds the valve ele ment 31 on the seat 34 but provides littleresistance against lifting of the valve from the seat for flow ofhydraulic fluid from the reservoir chamber 25 into the fluid receivingchamber of the cylinder tube 12.

The valve element 31 has an axial bore 36 that receives a valve element37 seated against the valve seat 38 by the compression spring 39, anaxial opening 40 providing for flow of hydraulic fluid from the lowerportion of the cylinder tube 12 against the upper side of the valve 37through a radial slot 29. The compression spring 39 controls the pointof opening of the valve 37.

The upper end of the shock absorber carries a resilient seal member 41that is retained between the cap member 22 and a seal ring 43 that isspring-urged against the seal 41 by means of a compression spring 42.The seal 41 prevents leakage of hydraulic fluid from around the rod 13.Any hydraulic fluid passing upwardly along the rod 13 through the guidemember 16 is returned to the reservoir chamber 25 through passage 44.

A piston 50 reciprocatingly slidable in the cylinder 12 is carried onthe lower end of the actuating rod 13, the piston having suitable valvepassages to control flow of hydraulic fluid through the piston andbetween the compression chamber 51 and the rebound chamber 52 definedwithin the cylinder 12 by the position of the piston therein.

The piston 50 has a valve assembly 55 on one end there-- of effectiveduring the compression stroke of the shock absorber and a valve assembly60 that is effective during the rebound stroke. The valve assembly 55comprises a valve disk 61 that is positioned upon a pair of annularlyarranged annular valve seats 62 and 63 on one end of the piston 50. Anannular recess 64 is provided between the valve seat 62 and 63, whichrecess communicates with outboard passages 65 extending therefrom to theopposite end of the piston. The series of fluid flow passages 65 providefor flow of hydraulic fluid from the compression chamber 51 to therebound chamber 52 under control of the valve 61. The piston 50 has asecond inboard series of fluid flow passages 68 providing for flow ofhydraulic fluid from the rebound chamber 52 to the compression chamber51 through ports in the valve disk 61 and under control of the valve 60.A compression spring 70 controls the opening point of valve 60 while adisk spring 72 controls the opening point of valve 61.

The shock absorber thus far described will function in a substantiallynormal manner wherein movement of the piston 50 toward the base valve 14will place fluid under compression in the chamber 51 on the compressionstroke, excess fluid that is not displaced into the rebound chamber 52through the valve 61 being discharged under pressure through the basevalve 14 under control the valve element 37. The volume of fluid flowthrough the base valve 14 is equivalent to the displacement of rod 13that enters the rebound chamber 52. On the return stroke or reboundstroke, fluid will flow from the rebound chamber 52 into the compressionchamber 51 under control of the valve 60. Make-up fluid to fill thechamber 51 on movement of the piston 50 away from the base valve 14 willbe received from the reservoir 25 through the bore 32 of the closurewall 27, valve element 31 opening against the disk spring 35 for thispurpose.

Prior art combinations of shock absorbers with rotating drums utilizeshock absorbers which are active to dampen vibrations of the rotatingdrum or vibrating mass throughout an entire range of rotational speeds,whether or not damping is desirable or needed. In other words, the priorart shock absorber combinations were effective to dampen the dangerouslarge excursions of the vibrating system 17 as the mass passed throughits resonant frequency as well as the harmless small vibrationsoccurring after the mass arrived at its normal operational spin speed orfrequency. Since any damping action expends energy and the only input tothe system is through the motor 11, such prior art arrangements requireoverly large motors 11.

The method of this invention in reducing the power required to drive adamped, elastically suspended, vibrating mass above the resonantfrequency of the vibrating system also reduces the transmissibility ofthe disturbing force because the reduction of damping force reduces thedamping factor of the hydraulic shock absorbers 9.

The novel combination of this invention incorporates a frequencysensitive by-pass valve or inertia valve assembly, shown generally at80, which is designed so that its own natural resonant frequency is thesame as the operational frequency of the vibrating mass. Assuming thecombination washer-dryer 6, for instance, has a maximum drum spin speedof 650 r.p.m. during centrifuging, the frequency sensitive by-pass valveassembly will be designed with a natural frequency of 650 cycles perminute. In this Wa the by-pass valve assembly 80 is effective to renderthe shock absorber ineffective at drum speeds above the resonantfrequency of the vibrating system 17, which, in the case of thecombination washerdryer 6, is approximately 160 c.p.m. Thus, the shockabsorber is effective to dampen large excusions of the vibrating systemas the drum 10 is accelerated through the resonant speed of 160 rpm.However, when system vibrations are small as the drum 10 reaches itsmaximum extraction speed of 650 r.p.m., the damping action of the shockabsorbers is effectively eliminated altogether and the drag on the motor11 is reduced proportionately.

More particularly, the frequency sensitive by-pass valve assembly 80 iscomprised of an inertia valve member 82 of inch C.D. steel weighing 0.1pound and reciprocatingly movable on a /8 inch OD. x 0.028 wall steeltubing valve guide 84 at one end of which is a inch diameter C.D. steelspring seat 86. The valve member 82 is urged by a first compressionspring 88 in one direction and by a second compression spring 90 in theopposite direction. Since the valve guide 84 has a pair of bypass ports92 at one end thereof and a pair of by-pass ports 94 at the other endthereof, the valve member 82 will be effective to open the ports 92 wheninertially shifted to its lowermost position (FIGURE 5) against therestraining bias of spring 90 and effective to open the ports 94 wheninertially shifted to its uppermost position (FIGURE 4) against therestraining bias of the spring 88. It should be understood that by-passport means could be established at one point only on the guide 84 byhaving the valve member 82 shift completely past the opening in eachdirection.

With the vibrating system 17 having a drum extraction speed of 650 rpm.and a resonant frequency of rpm, the frequency sensitive by-pass valveassembly 30 can be designed with the same natural frequency (650 cyclesper minute) if the spring 88 is made of music wire 0.040 inch indiameter having eight total turns, six of which are active turns, and afree length of l.200 inches. On the other hand, the opposing spring 90may be made of music wire 0.028 inch in diameter having seven totalturns, five of which are active turns, and a free length of 0.950 inch.

Anyone skilled in the art will know that calculations including thedimensions of springs 88 and 90 and valve member 82 will give a naturalfrequency of 900 cycles per minute. This is true in air, but when theassembly is built into a shock absorber as shown in FIGURE 3 and thepiston rod 13 cycles on a test machine, the test results will indicate anatural frequency of approximately 650 cycles per minute. Thispeculiarity can best be explained by saying that the effective mass ofvalve member 82 is not 0.1 pound but 0.1 pound plus the force producedby shock absorber fluid striking the end of the valve member at someappreciable velocity.

Cooperating with the bypass ports 92 or 94 is a passageway 96 throughthe actuating rod 13 which selectively interconnects the rebound chamber52 with the compression chamber 51 through the interior of the valveguide 84.

In operation, the valve member 82 will remain in its closed positionshown in FIGURE 3, moving in phase with the piston 50 and the ports 92,94 as the vibrating system 17 moves through its resonant frequency (drumspeed increasing from rpm. to 160 r.p.m.). During this time, the shockabsorber 9 will be effective to dampen the unbalance created excursionsof the vibrating system where needed. However, as the drum 10accelerates above its resonant speed of 160 r.p.m. to its maximum spinspeed of 650 r.p.m., the by-pass valve member 82 will start to partiallyuncover alternately ports 2 and 94 and will gradually increase its portuncovering travel until the valve member is vibrating at its own naturalfrequency of 650 cycles per minute but trailing 90 out of phase with thepiston St) at which point the drum 10 will be rotating at its top speedand the ports 92 and 94 will be alternately fully open. In other words,the valve 82, at its natural frequency, will be in its closed position(FIG- URE 3) whenever the piston 50 is at either extreme position in thecylinder 12. When the piston is at the midpoint of its travel in eitherdirection, however, the valve member 8'2. will be in one or the other ofits extreme positions (FIGURES 4 and 5), uncovering either the ports 94or 92 respectively to interconnect the compression chamber 51 with therebound chamber 52, thereby effectively eliminating the damping effectof the shock absorber 9.

As the drum decelerates at the conclusion of spin through its resonantfrequency at 160 rpm, the valve member 82 will again become effective togradually close the ports 92 and 94 so that the shock absorber will becompletely effective to dampen the large excursions of the unbalancedrotating mass at system resonant.

It should now be seen that an improved method has been provided forreducing power required to drive a damped, elastically suspended,vibrating mass above the resonant frequency of the system. Thecombination of a shock absorber having a frequency sensitive bypass witha rotating mass also reduces the transmissibility of the disturbingforce because the reduction of damping force reduces the damping factorof the hydraulic shock absorber. Power requirements are thus reduced inrotating systems, such as washing appliance spin drums, so that higherspin speeds are possible without increasing the size of the prime movertherefor.

While the embodiment of the present invention, as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted.

What is claimed is as follows:

1. In a clothes washing machine, the combination of means forming acasing, means in said casing defining a water container, a clothestumbling drum rotatably dis posed in said Water container means, meansfor rotating said tumbling drum about a non-vertical axis for extractingwater from clothes contained therein, said water container means,tumbling drum and rotating means defining a unitary system, means forelastically supporting said unitary system in said casing means formovement in vertical and horizontal directions, sa-id rotating meanseffecting rotation of said tumbling drum from standstill to anextracting speed above the resonant frequency of the elasticallysupported unitary system, and damping means comprising a hydraulic shockabsorber secured between said casing means and said water containermeans, said hydraulic shock absorber having a cylinder with areciprocable piston disposed therein dividing the cylinder into opposedchambers, the piston having passage means therethrough for effecting afirst flow path of hydraulic fluid between said opposed chambers whilesaid rotating means is accelerating said tumbling drum through theresonant frequency of said unitary system thereby to dampen thevibrations of said unitary system, and frequency sensitive by-pass meansin said cylinder having by-pass port means movable with said piston forselectively establishing a second flow path of hydraulic fiuid betweensaid opposed chambers and having valve means movable relative to saidport means 96 out of phase with said piston to open said port means forbypassing the flow of hydraulic fluid in said second flow path insteadof said first flow path While said rotatin means is rotating saidtumbling drum at said extracting speed, said valve means including aninertia actuated valve member and resilient means for elasticallysupporting said inertia valve member relative to said piston in a mannerto effect a natural frequency in said valve means equivalent to thevibratory frequency of said unitary system when said tumbling drum isrotated at said extracting speed.

2. In a washing machine, the combination of means forming a casing,means in said casing defining a liquid container, centrifuging meansrotatably disposed in said liquid container means, means for rotatingsaid centrifuging means about a non-vertical axis for extracting liquidfrom materials contained therein, said liquid container means,centrifuging means and rotating means defining a unitary system, meansfor elastically supporting said unitary system in said casing means formovement in a plurality of directions, said rotating means eifectingrotation of said centrifuging means from a speed below the resonantfrequency of the elastically supported unitary system to a speed abovesaid resonant frequency, and damping means comprising a shock absorbersecured between said casing means and said liquid container means, saidshock absorber having a tubular means with a reciprocable piston meansdisposed therein dividing the tubular means into opposed chambers, thepiston means having passage means therethrough for effecting a firstflow path of fluid between said opposed chambers while said rotatingmeans is rotating said centrifuging means at the resonant frequency ofsaid unitary system thereby to dampen the vibrations of said unitarysystem, and frequency sensitive by-pass means in said tubular meanshaving by-pass port means movable with said piston means for selectivelyestablishing a second flow path of fluid between said opposed chambersand having valve means movable relative to said port means out of phasewith said piston means to open said port means for by-passing the flowof fluid around said passage means while said rotating means is rotatingsaid centrifuging means at speeds above the resonant frequency of saidunitary system.

3. In a Washing machine, the combination of means forming a casing,means in said casing defining a liquid container, centrifuging meansrotatably disposed in said liquid container means, means for rotatingsaid centrifuging means about a non-vertical axis for extracting liquidfrom materials contained therein, said liquid container means,centrifuging means and rotating means defining a unitary system, meansfor elastically supporting said unitary system in said casing means formovement in a plurality of directions, said rotating means effectingrotation of said centrifuging means from a speed below the resonantfrequency of the elastically supported unitary system to a speed abovesaid resonant frequency, and damping means comprising a shock absorbersecured between said casing means and said liquid container means, saidshock absorber having a tubular means with a reciprocable piston meansdisposed therein dividing the tubular means into opposed chambers, thepiston means having passage means therethrough for effecting a firstflow path of fluid between said opposed chambers While said rotatingmeans is rotating said centrifuging means at the resonant frequency ofsaid unitary system thereby to dampen the vibrations of said unitarysystem, and frequency sensitive by-pass means in said tubular meanshaving by-pass port means movable with said piston means for selectivelyestablishing a second flow path of fluid between said opposed chambersand having valve means movable relative to said port means out of phasewith said piston means to open said port means for by-passing the flowof fluid around said passage means while said rotating means is rotatingsaid centrifuging means at speeds above the resonant frequency of saidunitary system, said valve means including a valve member and resilientmeans for elastically supporting said valve member relative to saidpiston means in a manner to effect a natural frequency in said valvemeans equivalent to the vibratory frequency of said unitary system whensaid centrifuging means is rotated above said resonant frequency of saidunitary system.

4. The combination of claim 3 wherein said resilient means includes apair of opposed spring supported for movement with said piston means andsandwiching said valve member therebetween in blocking engagement withsaid port means when said centrifuging means is rotated at the resonantfrequency of said unitary system.

5. In combination, means forming a casing, means rotatably supportedrelative to said casing defining a container, means for rotating saidcontainer means about a non-vertical axis, said container means androtating means defining a unitary system, means for elasticallysupporting said unitary system relative to said casing means formovement in a plurality of directions, said rotating means effectingrotation of said container means from a speed below the resonantfrequency of the elastically supported unitary system to a speed abovesaid resonant frequency, and damping means comprising a shock absorbersecured between said casing means and said container means, said shockabsorber having a tubular means with a reciprocab1e piston meansdisposed therein dividing the tubular means into opposed chambers, thepiston means having passage means therethrough for effecting a firstflow path of fluid between said opposed chambers while said rotatingmeans is rotating said container means at the resonant frequency of saidunitary system thereby to dampen the vibrations of said unitary system,and frequency sensitive by-pass means associated with said tubular meanshaving by-pass port means movable with said piston for selectivelyestablishing a second flow path of fluid between said opposed chambersand having valve means movable relative to said port means out of phasewith said piston means to open said port means for by-passing the flowof fluid around said passage means while said rotating means is rotatingsaid container means at speeds above the resonant frequency of saidunitary system.

6. In combination, means forming a casing, means rotatably supportedrelative to said casing defining a container, means for rotating saidcontainer means about a non-vertical axis, said container means androtating means defining a unitary system, means for elasticallysupporting said unitary system relative to said casing means formovement in a plurality of directions, said rotating means effectingrotation of said container means from a speed below the resonantfrequency of the elastically supported unitary system to a speed abovesaid resonant frequency, and damping means comprising a shock absorbersecured between said casing means and said container means, said shockabsorber having a tubular means with a reciprocable piston meansdisposed therein dividing the tubular means into opposed chambers, thepiston means having passage means therethrough for effecting a firstflow path of fluid between said opposed chambers while said rotatingmeans is rotating said container means at a resonant frequency of saidunitary system thereby to dampen the vibrations of said unitary system,and frequency sensitive by-pass means associated with said tubular meanshaving by-pass port means movable with said piston for selectivelyestablishing a second flow path of fluid between said opposed chambersand having valve means movable relative to said port means out of phasewith said piston to open said port means for by-passing the flow offluid around said passage means while said rotating means is rotatingsaid container means at speeds above the resonant frequency of saidunitary system, said valve means including a valve member and resilientmeans for elastically supporting said valve member relative to saidpiston means in a manner to effect a natural frequency in said valvemeans equivalent to the vibratory frequency of said unitary system whensaid container means is rotated above said resonant frequency of saidunitary system.

7. In combination, means forming a casing, means rotatably supportedrelative to said casing defining a container, means for rotating saidcontainer means about a non-vertical axis, said container means androtating means defining a unitary system, means for elasticallysupporting said unitary system relative to said casing means formovement in a plurality of directions, said rotating means effectingrotation of said container means from a speed at the resonant frequencyof the elastically supported unitary system to a speed above saidresonant frequency, and damping means comprising an hydraulic shockabsorber secured between said casing means and said container means,said hydraulic shock absorber including first means responsive to thevibrations of said unitary system at said resonant frequency forresisting the excursions of said unitary system, second means responsiveto the vibrations of said unitary system at said speed above saidresonant frequency for preventing the effectiveness of said first means,and resilient means elastically supporting said second means relative tosaid first means in a manner to effect a natural frequency in saidsecond means equivalent to the vibratory frequency of said uni tarysystem when said container means is rotating at said speed above saidresonant frequency.

8. In combination, means forming a casing, means rotatably supportedrelative to said casing defining a container, means for rotating saidcontainer means about a non-vertical axis, said container means androtating means defining a unitary system, means for elasticallysupporting said unitary system relative to said casing means formovement in a plurality of directions, said rotating means effectingrotation of said container means from a speed at the resonant frequencyof the elastically supported unitary system to a speed above saidresonant frequency, and damping means secured between said casing meansand said container means, said damping means including first meansresponsive to the vibrations of said unitary system at said resonantfrequency for resisting said vibrations when said container means isrotating at said speed at said resonant frequency, second meansresponsive to the vibrations of said unitary system at said speed abovesaid resonant frequency to negate the effectiveness of said first means,and resilient means elastically supporting at least a portion of saidsecond means in a manner to effect a natural frequency in said portionof said second means equivalent to the vibratory frequency of saidunitary system when said container means is rotating at said speed abovesaid resonant frequency.

9. In combination, means forming a casing, means rotatably supportedrelative to said casing defining a container, means for rotating saidcontainer means about a non-vertical axis, said container means androtating means defining a unitary system, means for elasticallysupporting said unitary system relative to said casing means formovement in a plurality of directions, said rotating means effectingrotation of said container means from a speed below the resonantfrequency of the elastically supported unitary system to a speed abovesaid resonant frequency, and damping means comprising a shock absorbersecured between said casing means and said container means, said shockabsorber having a tubular means with a movable piston means disposedtherein dividing the tubular means into opposed chambers, the pistonmeans having passage means 'therethrough for effecting a first flow pathof fluid between said opposed chambers while said rotating means isrotating said container means at the resonant frequency of said unitarysystem thereby to dampen the vibrations of said unitary system, and frequency sensitive by-pass means associated with said tubular means havingby-pass port means for selectively establishing a second flow path offluid between said opposed chambers and having valve means movable rela-15 References Cited in the file of this patent UNITED STATES PATENTS1,268,452 Goodyear June 4, 1918 10 2,642,996 Oeler et al. June 23, 1953FOREIGN PATENTS 877,164 Great Britain Sept. 13, 1961 1,048,137 FranceJuly 29, 1953

8. IN COMBINATION, MEANS FORMING A CASING, MEANS ROTATABLY SUPPORTED RELATIVE TO SAID CASING DEFINING A CONTAINER, MEANS FOR ROTATING SAID CONTAINER MEANS ABOUT A NON-VERTICAL AXIS, SAID CONTAINER MEANS AND ROTATING MEANS DEFINING A UNITARY SYSTEM, MEANS FOR ELASTICALLY SUPPORTING SAID UNITARY SYSTEM RELATIVE TO SAID CASING MEANS FOR MOVEMENT IN A PLURALITY OF DIRECTIONS, SAID ROTATING MEANS EFFECTING ROTATION OF SAID CONTAINER MEANS FROM A SPEED AT THE RESONANT FREQUENCY OF THE ELASTICALLY SUPPORTED UNITARY SYSTEM TO A SPEED ABOVE SAID RESONANT FREQUENCY, AND DAMPING MEANS SECURED BETWEEN SAID CASING MEANS AND SAID CONTAINER MEANS, SAID DAMPING MEANS INCLUDING FIRST MEANS REPONSIVE TO THE VIBRATIONS OF SAID UNITARY SYSTEM AT SAID RESONANT FREQUENCY FOR RESISTING SAID VIBRATIONS WHEN SAID CONTAINER MEANS IS ROTATING AT SAID SPEED AT SAID RESONANT FREQUENCY, SECOND MEANS RESPONSIVE TO THE VIBRATIONS OF SAID UNITARY SYSTEM AT SAID SPEED ABOVE SAID RESONANT FREQUENCY TO NEGATE THE EFFECTIVENESS OF SAID FIRST MEANS, AND RESILIENT MEANS ELASTICALLY SUPPORTING AT LEAST A PORTION OF SAID SECOND MEANS IN A MANNER TO EFFECT A NATURAL FREQUENCY IN SAID PORTION OF SAID SECOND MEANS EQUIVALENT TO THE VIBRATORY FREQUENCY OF SAID UNITARY SYSTEM WHEN SAID CONTAINER MEANS IS ROTATING AT SAID SPEED ABOVE SAID RESONANT FREQUENCY. 